Benjamin made this model from 1946 to 1985, but did not start serializing them until 1957. I also have a Benjamin Franklin that has no serial number. Before 1957 it is not possible to set an exact date. Just know it's OLD. The 137 is a .177 caliber pellet pistol the 132 is a .22 caliber pistol and the 130 is a BB pistol.
Which Model are you asking about.
The model 132 was made from 1942 to 1986.
The model 100 was made between 1935-1941.
T427432 was made in 1982.
It's usually on the breech or the very back of the pistol.
It started in 1946 to 1985
It was made sometime between 1969-92.
Around $50
Auction
It would be worth between $60 and $80.
The Model 122 is a .22 caliber pellet pistol, not a BB or .177 caliber pistol. Pump up the pistol, Not more than 10 pumps. Open the breech by turning the knob at the rear. Pull it all the way back. Load the .22 pellet in the breech. The skirt faces the rear. Close the breech. Rotate the knob to lock it in place. Aim, release the safety and fire.